In the design and construction of buildings, a variety of architecture requirements and building codes must be considered. External elements are one of many factors to be addressed. For example, construction joints in various structures are often required to be sealed, ensuring a compartment within a building structure is protected from air or water transfer. If the construction is fire-resistant rated, a seal may also be required to have insulation properties and/or be fire resistant to contain a fire in the area of origin. A seal of this type prohibits the spread of the fire, for example, from the floor of origin to another floor. Although the fire could spread in any direction, in a floor seal the anticipated fire exposure is conventionally assumed from the bottom in test standards.
One type of conventional seal is formed within an expansion joint. For example, the seal may be formed in a void between two floor sections, such as opposing concrete sections. This type of seal can be made by a backer rod inserted into the void to a desired depth, with an amount of sealant placed on top of the backer rod. As such, the position of the backer rod acts to control the depth of the sealant within the void. Backer rods can also be installed between concrete sections of a sidewalk. Similar to installation between floor sections, the backer rod in a sidewalk serves as a depth control for a sealant.
For standard construction joints that are not fire-resistant rated, it is typical to use a closed-cell polyethylene foam backer rod between the two surfaces. An exemplary backer rod of this type is discussed in U.S. Pat. No. 6,997,640 to Hohmann, Jr. The patent describes a backer rod with a service temperature range up to 450 degrees Fahrenheit. A backer rod with this characteristic would not be regarded as fire resistant. Specifically, fire tests performed in accordance with industry standards generate a 450 degree temperature exposure within 5 minutes after the start of a test. Present and accepted industry testing requirements for fire resistance are detailed in (1) ASTM E1966 Standard Test Method for Fire-Resistive Joint Systems and (2) ANSI/UL 2079 Tests for Fire Resistance of Building Joint System). In other words, fire resistant rated joints between construction elements require a more substantial insulation barrier at elevated temperatures.
Conventionally, a fire resistant joint has been obtained using a slag mineral wool or a ceramic fiber as the depth control medium. These products have a high tolerance to heat exposure and limit heat transfer by maintaining their structure when exposed to the extreme temperatures of a fire test, which can be as high as 2000 degrees Fahrenheit for a 4 hour exposure test.